We synthesized azobenzene-conjugated bis(terpyridine) Ru(II) and Rh(III) mononuclear and dinuclear complexes and investigated their photochemical properties on excitation of the azo pi-pi band upon 366 nm light irradiation. The Ru mononuclear complex underwent trans-to-cis photoisomerization to reach the photostationary state with only 20% of the cis form, while the Ru dinuclear complex did not isomerize at all photochemically. On the other hand, the mononuclear and dinuclear Rh complexes showed almost complete trans-to-cis photoisomerization behavior. Cis forms of the Rh complexes thermally returned to the trans form at a much slower rate than those of organic azobenzenes, but they did not isomerize photochemically. The reduction potential of the cis forms was 80 mV more negative than that of the trans forms. The photoisomerization quantum yields of the Rh complexes were strongly dependent on the polarity, viscosity, and donor site of the solvents as well as the size of the counterions. We investigated the photoisomerization process of these complexes using femtosecond absorption spectroscopy. For the Rh complexes, we observed S(n) <-- S(2) and S(n) <-- S(1) absorption bands similar to those of organic azobenzenes. For the Ru complexes, we observed very fast bleaching of the MLCT band of the Ru complex, which indicated that the energy transfer pathway to the MLCT was the primary cause of the depressed photoisomerization. The electronic structures, which were estimated from ZINDO molecular orbital calculation, supported the different photochemical reaction behavior between the Ru and Rh complexes.

Palladium nanoparticles protected by alkanethiolates with a core diameter 1.3-3.9 nm were synthesized by the treatment of PdCl2(CH3CN)2 with tetraalkylammonium bromide and LiBEt3H in THF, followed by the addition of alkanethiols. The mean size and its deviation as observed by transmission electron microscopy varied in relation to changes in the reaction conditions involving variables such as the ammonium salt, the molar ratio of the reactants, the reaction time, and the alkanethiol. Smaller particles were obtained when the ratio of [PdCl2(CH3CN)2] to other reagents was decreased, the reaction time was increased, and a long alkanethiol was used.

New azo-bridged ferrocene trimers, Fc-Fc'-N=N-Fc (2) and Fc-N=N-Fc'-N=N-Fc (3), where Fc and Fc' refer to (eta(5)-C(5)H(5))Fe(eta(5)-C(5)H(4)-) and Fe(eta(5)-C(5)H(4)-)(2), respectively, were obtained in the reaction of a mixture of lithioferrocene and 1,1'-dilithioferrocene with N(2)O. X-ray crystallography of azoferrocene (1) has determined that the Fe-Fe distance is 6.80 Å in the trans form. Cyclic voltammograms of 3 in aprotic solvents such as CH(2)Cl(2) or THF exhibit reversible 2e(-) and 1e(-) oxidation waves, indicating that the positive charge in the monocation is localized mostly on the terminal ferrocene unit (correspondingly, Fc(+)-N(2)-Fc'-N(2)-Fc) due to a strong electron-withdrawing effect of the azo group. This charge distribution in the mixed-valence state is supported by the characteristics of intervalence-transfer (IT) bands. An asymmetrical complex, 2, undergoes a three-step 1e(-) oxidation, and the two mixed-valence forms can be roughly expressed as Fc(+)-Fc'-N(2)-Fc and Fc(+)-Fc'-N(2)-Fc(+). The redox potentials and IT band characteristics of 1(+), 2(+), and 2(2+) depend markedly on the solvent. The solvent effect of the IT band on nu(max) cannot be interpreted only by the parameters in the Marcus-Hush theory, indicating that the nature of the solvent as donor or acceptor should be taken into account in the electron-exchange process in the mixed-valence states. More donating solvent affords higher IT and LMCT energy, indicating the hole-transfer mechanism. The reaction of 1,1'-dilithioferrocene and N(2)O gives a polymer composed of [-(Fc'-N=N-Fc')(0.6)-(Fc'-Fc')(0.4)-](n)().

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